Pneumocystis jirovecii:
Pneumocystis jirovecii is an opportunistic fungal pathogen that causes pneumonia in immunocompromised individuals. Although historically misclassified as a protozoan, it is now recognized as a fungus based on molecular and genetic characteristics. Unlike most fungi, P. jirovecii lacks ergosterol in its cell membrane and cannot be cultured using standard laboratory media. It resides in the alveoli of the lungs, where it attaches to epithelial cells and interferes with gas exchange.

Diseases caused by Pneumocystis jirovecii:
The primary disease caused by P. jirovecii is Pneumocystis pneumonia (PCP), a serious and potentially fatal infection, especially in individuals with weakened immune systems, such as those with HIV/AIDS, cancer, or organ transplants. Symptoms of PCP include progressive shortness of breath, non-productive cough, fever, and fatigue. Without prompt treatment, the infection can cause severe hypoxia and respiratory failure.

Detection and Diagnosis of Pneumocystis jirovecii:
Diagnosis of P. jirovecii infection typically involves a combination of clinical evaluation and laboratory testing. Microscopic identification using special stains (such as silver stain or immunofluorescence) on respiratory specimens can visualize the organism. Polymerase chain reaction (PCR) assays are highly sensitive and can detect P. jirovecii DNA in bronchoalveolar lavage fluid or sputum. Serological tests, including enzyme-linked immunosorbent assays (ELISA), like those available here, can detect antibodies or antigens related to P. jirovecii infection, aiding in research and surveillance. Early diagnosis is crucial for initiating treatment and preventing complications in vulnerable populations.